Magnetic read head with antiferromagentic layer

ABSTRACT

A tunnel magnetoresistance (TMR) read sensor having a tabbed AFM layer and an extended pinned layer and methods for making the same are provided. The TMR read sensor has an AFM layer recessed from the air bearing surface, providing a reduced shield-to-shield distance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 14/230,962 (Atty. Docket No. F6672), filed Mar. 31, 2014, which claims the benefit of U.S. Provisional Application Ser. No. 61/894,550 (Atty. Docket No. F6672.P), filed Oct. 23, 2013, which are incorporated herein by reference in their entireties.

BACKGROUND

In magnetic storage devices such as hard disk drives (HDD), read and write heads are used to magnetically read and write information to and from storage media. In a HDD, data may be stored on one or more disks in a series of adjacent concentric circles which may be referred to as data tracks. A HDD may include a rotary actuator, a suspension mounted on an arm of the rotary actuator, and a slider bonded to the suspension to form a head gimbal assembly (HGA). In a traditional HDD, the slider carries a write head and read head, and radially slides over the surface of the storage media, e.g., a disk, under the control of a servo control system that selectively positions a head over a specific track of the disk. In this one read head (reader) configuration, the reader is aligned over the center of a track for data read back.

As HDD storage capacities have increased, the data track separation has decreased and the density has increased. Increasing magnetic recording density entails narrower-track widths and narrower shield-to-shield (S-S) spacing on the read heads. Current tunnel magnetoresistance (TMR) read heads can include among other elements, a pinned layer coupled to an antiferromagnet (AFM) layer. The TMR read heads may further comprise a free layer separated from the pinned layer by a barrier layer. In current perpendicular magnetic recording (PMR) read heads, little room exists, if any, to further reduce S-S spacing due to the existence of the AFM pinning material underneath the pinned layer. Attempts to narrow the S-S spacing by removing the AFM layer have been unsuccessful because AFM-free TMR read heads are prevalently magnetically bi-directional.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not limitation, in the figures of the accompanying drawings in which:

FIG. 1 illustrates a conventional read sensor;

FIG. 2 is an operational flow chart illustrating example processes performed in accordance with various embodiments for manufacturing a TMR read sensor;

FIGS. 3A-3D illustrate various fabrication stages of a TMR read sensor in accordance with various embodiments;

FIG. 4A and 4B illustrate an example TMR read sensor in accordance with one embodiment; and

FIGS. 5A-5C illustrate additional example TMR read sensors in accordance with various embodiments.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth, such as examples of specific layer compositions and properties, to provide a thorough understanding of various embodiment of the present invention. It will be apparent however, to one skilled in the art that these specific details need not be employed to practice various embodiments of the present invention. In other instances, well known components or methods have not been described in detail to avoid unnecessarily obscuring various embodiments of the present invention.

The terms “over,” “under,” “between,” and “on” as used herein refer to a relative position of one media layer with respect to other layers. As such, for example, one layer disposed over or under another layer may be directly in contact with the other layer or may have one or more intervening layers. Moreover, one layer disposed between two layers may be directly in contact with the two layers or may have one or more intervening layers. In contrast, a first layer “on” a second layer is in contact with that second layer. Additionally, the relative position of one layer with respect to other layers is provided assuming operations are performed relative to a substrate without consideration of the absolute orientation of the substrate.

In a conventional TMR read sensor, such as TMR read sensor 100 illustrated in an air bearing surface (ABS) perspective view of FIG. 1, a first shield layer, S1, may be disposed over a substrate. First shield layer S1 may comprise a Nickel Iron (NiFe) alloy, also referred to as permalloy, or another magnetic shield material for TMR read sensors. In some cases, first shield layer S1 may be composed of a single shield material. In other cases, first shield layer S1 may have a composite structure. For example, first shield layer S1 may comprise one or more layers of NiFe, NiFe multilayers, Cobalt Iron (CoFe), or Ruthenium (Ru).

Atop first shield layer S1, a seed layer may be disposed, as well as an AFM layer. The seed layer may comprise Tantalum (Ta), Ru, a Ta/Ru bilayer or other conventional seed layer(s). The AFM layer may comprise various antiferromagnetic materials, such as IrMn, Platinum Manganese (PtMn), Palladium Manganese (PdMn), Nickel Manganese (NiMn), Rhodium Manganese (RhMn), or RhRuMn. IrMn is often used in TMR AFM layers because it provides a thinner AFM layer than other materials.

Additionally, an AFM pinned layer may be disposed on the seed layer. The AFM pinned layer is magnetically pinned by the AFM layer in a particular direction, and may comprise a first pinned layer P1 of CoFe that provides a material transition between the AFM layer and a second pinned layer P2. In other cases, the pinned layer may comprise a tri-layer of a first layer of a soft magnetic material such as CoFe, a second layer of Ru, Cr, Ag, or Au, or other suitable non-magnetic material, and a third layer of soft magnetic material, such as CoFe.

TMR read sensor 100 further comprises a free layer separated from the pinned layer by a barrier layer and separated from a second (top) shield layer, S2, by a capping layer. The free layer comprises a ferromagnetic material, such as NiFe, CoFe, or CoNiFe. The barrier layer comprises an insulating material, and may be selected to provide a seed layer for the free layer. For example, Magnesium Oxide (MgO) may be used as the barrier layer. The capping layer isolates the free layer from the top shield layer and comprises a non-magnetic material, such as Ru, Ta, or a bilayer thereof. Top shield S2 is disposed over the TMR read sensor layers, and may also comprise NiFe or other conventional material for TMR read sensors. For example, top shield S2 may have a composition similar to the first shield S1. Further still, TMR read sensor 100 may include antiferromagnetic-coupled soft bias (AFC SB) structures for magnetically biasing the free layer. As illustrated in FIG. 2, the S-S is the distance between the first shield S1 and the second shield S2 at the ABS, which in this conventional example is approximately 25-26 nm.

In accordance with various embodiments, a read head architecture and fabrication method to enable ultra-thin S-S spacing is provided. In various embodiments, the AFM pinning layer, which may include Iridium Manganese (IrMn), may be removed from the bottom of a pinned layer of the TMR film stack, hence reducing the two shield separation, while tabbing the AFM pinning layer to either side of the remaining TMR film stack but underneath the “extended” pinned layer. A read head manufactured to have such an architecture in accordance with various embodiments may retain stronger AFM pinning strength and may be easier to fabricate, where such embodiments may be provided for 1 Tb/in² ultra high density magnetic recording heads at sub-20 nm thin S-S spacing.

FIG. 2 is an operational flow chart illustrating an example method 200 that can be performed to manufacture a TMR read sensor having an ultra-thin S-S spacing in accordance with various embodiments. Method 200 may begin with operation 210, wherein a first shield layer is formed. The first shield layer may have a single shield material structure or a composite structure. The first shield layer may comprise one or more layers of NiFe, NiFe multilayers, CoFe, or Ru. At operation 220, a seed layer is deposited on the first shield layer. The seed layer may comprise Ta, Ru, a Ta/Ru bilayer or other conventional seed layer(s). At operation 230, a tabbed AFM stack layer is formed over the seed layer. The tabbed AFM stack layer may comprise various antiferromagnetic materials, such as IrMn, PtMn, PdMn, NiMn, RhMn, or RhRuMn. At operation 240, pinned layers are formed over the AFM stack layer. The pinned layers may have, e.g., a tri-layer structure where first and second pinned layers may be CoFe with a non-magnetic material such as Ru, Cr, Ag, or Au, or other suitable non-magnetic material, separating the first and second pinned layers. At operation 250, a free layer is formed over the pinned layers. The free layer may comprise a non-magnetic material, such as Ru, Ta, or a bilayer thereof. At operation 260, a second shield layer is formed. The second shield layer may have a single shield material structure or a composite structure. The second shield layer may comprise one or more layers of NiFe, NiFe multilayers, CoFe, or Ru.

In accordance with various embodiments, an AFM layer may be positioned on either side of the read track, which is recessed into the first shield layer and serves as a bottom tab to the pinned layer. As will be described below, in some embodiments, the AFM layer may be substantially U-shaped or horseshoe-shaped. However, in other embodiments, the AFM layer may take on other shapes/configurations, e.g., a semi-circular shape, so long as the desired ultra-thin S-S spacing can be maintained. The AFM tab may be formed using a mask similar to that of a hard bias mask but with a center track that is wider than the reader TW. Such an architecture may yield much thinner S-S spacing that conventional structures. In one embodiment, the S-S spacing is approximately 7 nm thinner while the pinned layer is still magnetically pinned by the AFM pinning layer beneath the pinned layer on both sides.

FIGS. 3A-3D illustrates various fabrication stages in accordance with one embodiment, FIG. 3A illustrates a fabrication stage wherein the seed layer 320 is deposited on the first shield layer 310, seed layer 320 comprising CoFeB10 Å/NiFe50 Å/Ta10 Å/Ru60 Å. A photolithography process may be used to define the AFM tab area with a mask similar to a hard bias mask but with a wider center track so as to leave sufficient amount of the first shield layer 310 to retain its shielding properties. Ion milling may then be applied to remove the exposed seed layer 320 to generate a recess as illustrated in FIG. 3B, followed by AFM stack deposition of Ta10 Å/Ru60 Å/IrMn80 Å/CoFe100 Å by either in situ ion beam deposition or ex situ physical vapor deposition (PVD) as illustrated in FIG. 3C, where AFM layer 340 (IrMn) and soft magnetic stitching layer 350 (CoFe) are shown. That is, the AFM layer (i.e., AFM tabbed areas) may be placed on either side of a read track, which can serve as a bottom tab to the pinned layer, where the AFM tab has a center track that is wider than the reader track width. In situ ion beam deposition can refer to AFM film stack deposition immediately after milling of the TMR seed layer without breaking vacuum. Ex situ PVD can refer to performing TMR seed layer milling and AFM film stack deposition in separate runs/stages with air exposure between the stages. After photoresist 330 liftoff, glazing angle milling may be used for surface planarization to create a flat and smooth surface for the AFM-free TMR stack deposition. The deposition may be carried out in a sputtering chamber and the TMR stack, P1/Ru/P2 (360) MgO/FL (370)/Cap (380), may be seamlessly stitched onto the formed AFM bottom tab as illustrated in FIG. 3D. A relatively flat and smooth interface between the AFM tab and TMR stack results from the above process, and a standard reader process can be followed, such as, magnetic annealing, reader junction formation, SB depositions, etc. It should be noted that strong AFM pinning between the AFM tab and the pinned layer results, as well as strong antiferromagnetic coupling (AFC) between the P1 and P2 layers of the pinned layer. It should also be noted that the reader junction forms via ion beam partial milling to generated the extended pinned layer along the ABS direction, which is pinned by the underlying AFM tab from both sides.

FIGS. 4A-4B illustrate an example TMR read sensors manufactured to have an architecture enabling ultra-thin S-S spacing in accordance with various embodiments. FIGS. 4A and 4B illustrate a TMR read sensor 400, where the AFM pinning layer 420 is substantially U-shaped or horseshoe-shaped. In one embodiment the AFM pinning layer 420 is IrMn, and may be disposed over shield 410-1. Over AFM pinning layer 420, a pinned layer can be deposited. In this example, the pinned layer includes first and second pinned layers 430 and 440, respectively, along with a non-magnetic material 435 resulting in, e.g., a tri-layer structure. A barrier layer 450 may be disposed over the pinned layer, and barrier layer 450 may be, e.g., MgO. TMR read sensor 400 may also include free layer 460 and shield 410-2, as well as AFC SB structure 470. As can be appreciated, the S-S spacing between shields 410-1 and 410-2 may be reduced as a result of AFM pinning layer 420 having a U-shape.

FIGS. 5A-5C illustrate still other example TMR read sensor structures manufactured in accordance with various embodiments to have an ultra-thin S-S spacing. FIG. 5A illustrates a TMR read sensor 500 a having a first shield layer 510-1 and a substantially U-shaped AFM pinning layer 520, AFM pinning layer 520 being IrMn. Disposed over AFM pinning layer 520 is a pinned layer, having a tri-layer structure (e.g., P1 530/Ru 535/P2 540). However, a center portion of the P1 530 layer may have a substantially trapezoidal-like ABS perspective cross-section (center read track) upon which a barrier layer 550 and free layer 560 (each of which also have a substantially trapezoidal-like ABS perspective cross-section may be deposited. TMR read sensor 500 a further includes AFC SB structure 570 and second shield layer 510-2. It should be noted that there is a distance of at least 30 nm between the respective edges of the U-shaped AFM layer 520 and the center portion of the TMR stack. In accordance with one embodiment, first shield layer 510-1 of TMR read sensor 500 a may include a plurality of thin non-magnetic layers 525 (two in this example). Thin non-magnetic layers 525 can be Ru, Cr, or other non-magnetic material, each having a thickness of between, e.g., 5 Å to 20 Å. At high frequencies, the first shield layer 510-1 (e.g., of permalloy/NiFe) permeability may not be optimal. Accordingly, non-magnetic layers 525 can be used to laminate first shield layer 510-1, which results in much higher permeability, leading to better shielding characteristics/effectiveness.

FIG. 5B illustrates a TMR read sensor 500 b having a first shield layer 510-1 and a second shield layer 510-2. Deposited on the first shield layer 510-1 is the AFM layer 520. Disposed over the AFM layer 520 is a substantially U-shaped first pinned layer including pinned layers 530-1 and 530-2. Deposited over the first pinned layer is a second pinned layer including pinned layers 530-3 and 530-4 separated by, e.g., a Ru layer 535. Deposited on the second pinned layer can be a barrier layer 550 of MgO and a free layer 560. Similar to FIG. 5A, AFC SB structure 570 may be disposed on the second pinned layer over which second shield layer 510-2 is disposed. The distance between the edge of free layer 560 and AFM layer 520 can be 30-50 nm.

It should be noted that only a few junction fabrication process and stack arrangement differences between the TMR read sensor 500 a of FIG. 5A and the TMR read sensor 500 b of FIG. 5B. The three-dimensional AFM (IrMn) layer shapes are the same, however, and in both cases, the cross track distance between the outer edge of the free layer and the edge of the FM layer is approximately 100 nm.

FIG. 5C illustrates yet another TMR read sensor 500 c manufacture in accordance with various embodiments having a first shield layer 510-1 on which a seed layer 515 is disposed. A substantially U-shaped AFM pinning layer 520, AFM pinning layer 520 being IrMn, may be disposed over the seed layer 515 and first shield layer 510-1. Disposed over AFM pinning layer 520 is a pinned layer, having a tri-layer structure (e.g., P1 530/Ru 535/P2 540). However, a center portion of the P1 530 layer may have a substantially trapezoidal-like ABS perspective cross-section upon which a barrier layer 550 and free layer 560 (each of which also have a substantially trapezoidal-like ABS perspective cross-section may be deposited. TMR read sensor 500 a further includes AFC SB structure 570, and a second shield layer 510-2 that includes another AFM layer 575. Similar to TMR read sensor 500 a, second shield layer 510-2 may further include a thin non-magnetic layer 565, such as Ru, Cr, etc., which can have a thickness between, e.g., 3.5 Å to 9 Å.

Although described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations, to one or more of the other embodiments of the application, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus, the breadth and scope of the present application should not be limited by any of the above-described exemplary embodiments.

Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as meaning “including, without limitation” or the like; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof; the terms “a” or “an” should be read as meaning “at least one,” “one or more” or the like; and adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future Likewise, where this document refers to technologies that would be apparent or known to one of ordinary skill in the art, such technologies encompass those apparent or known to the skilled artisan now or at any time in the future.

The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent. The use of the term “module” does not imply that the components or functionality described or claimed as part of the module are all configured in a common package. Indeed, any or all of the various components of a module, whether control logic or other components, can be combined in a single package or separately maintained and can further be distributed in multiple groupings or packages or across multiple locations.

Additionally, the various embodiments set forth herein are described in terms of exemplary block diagrams, flow charts and other illustrations. As will become apparent to one of ordinary skill in the art after reading this document, the illustrated embodiments and their various alternatives can be implemented without confinement to the illustrated examples. For example, block diagrams and their accompanying description should not be construed as mandating a particular architecture or configuration. 

What is claimed is:
 1. A magnetic read head, comprising: a first shield layer; a seed layer deposited on the first shield layer; a tabbed antiferromagnetic (AFM) stack layer formed over the seed layer, wherein the tabbed AFM stack layer is recessed along both sides of a read track of the magnetic read head; first and second pinned layers formed over the AFM stack layer; a free layer formed over the first pinned layer; and a second shield layer formed over the first pinned layer.
 2. The read head of claim 1, wherein the tabbed AFM stack layer comprises: an AFM layer; and a soft magnetic stitching layer.
 3. A hard disk drive, comprising: at least one rotatable disk having a disk surface; a disk drive base; a spindle motor attached to the disk drive base and configured to support the disk for rotating the disk with respect to the disk drive base surface; and a magnetic reader configured to read data on the rotatable disk surface, the magnetic reader comprising: a first shield layer; and a seed layer deposited on the first shield layer; a tabbed antiferromagnetic (AFM) stack layer formed over the seed layer, wherein the tabbed AFM stack layer is recessed along both sides of a read track of the magnetic reader; first and second pinned layers deposited over the AFM stack layer; a free layer deposited over the first pinned layer; and a second shield layer deposited over the first pinned layer.
 4. The hard disk drive of claim 3, wherein the magnetic reader comprises a tunneling magnetoresistance (TMR) reader. 